Multiple ply tubes and particularly multiple ply paperboard or cardboard tubes, are widely used in industry for a variety of purposes. Typically, the multiple layer tubes are made from a plurality of continuous plies which are helically wound about a stationary mandrel. The separate ply strips are fed from separate reels through a glue bath to a stationary mandrel. The plies are then wound helically on the mandrel, one on top of another. An endless belt rotates and advances the formed tube around and along the stationary mandrel. At the downstream end of the mandrel, a severing device cuts the endless tube into separate tubes of a predetermined length.
Helically wound tubes made in this manner have diameters ranging from about 1 inch up to 48 inches or more. These tubes have walls including from 1-2 plies up to 20 plies or greater. Particularly when multiple plies, for example 3 or more plies, are used to form a helically wound tube, the outer diameter of the tube can vary along the tube length.
Variations in the outer diameter of the tube are highly undesirable particularly in some tube applications. When the tubes are used as cores for the high speed winding of textiles, paper, plastic films and the like, a highly uniform and highly controlled outside tube diameter is of significant importance because the winding speed is determined in part by the outer diameter of the tube. In addition, in some film and textile operations, multiple textile and film packages are wound simultaneously on a single mandrel. Unless the outer diameter of the multiple tube cores on the single mandrel are identical, the winding speed will vary from core to core.
Various proposals have been made in the art for improving the uniformity of the outside diameter of paperboard tubes. For example, U.S. Pat. No. 1,849,111 to Parker proposed that a circular series of fingers be provided for pressing inwardly against the outer surface of a tube being wound on a mandrel. The fingers were said to engage the tube over an axial length of a few inches. The tube was said to be fed along so that each successful pinch was a short distance further along the tube. The tube was said to thus be compressed from end to end.
A different proposal for accurately made in U.S. Pat. No. 3,580,146. According to the proposal of this patent, helically wound multi-layer cardboard tubes were said to be wound with one of the layers being a low density material which was substantially compressible in the radial direction. The as-formed tube was externally coated with a thermosetting resin, cut into predetermined lengths and dried. Subsequently, the rough tubes were forcibly inserted through the bore of a heated matrix to reduce the circumference of the tube to a desired precise diameter and cause polymerization of the resin coating.
These proposals for accurately controlling the outside diameter of paperboard tubes result in various difficulties including the interference with the winding operation and/or the need for additional manufacturing steps and apparatus. Such requirements increase the complexity and expense of manufacturing the paperboard tubes. Nevertheless, as winding speeds have increased in textile, film and other manufacturing operations, the need for accurately controlling the outside diameter of paperboard tubes has increased.